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A new analysis of tree-ring data indicates that the climate cycle known as the El Niño – Southern Oscillation (ENSO) has been more active during the latter part of the 20th century than at any other time during the past seven centuries, suggesting that global warming is affecting this climate phenomenon. Using data from 2,222 tree-ring chronologies from the tropics and mid-latitudes in both the northern and southern Hemispheres, a team of scientists determined that ENSO-related behavior in the late 20th century was far greater than the natural variability reflected in data going back to 1300. A naturally occurring climate cycle, ENSO is characterized by warmer ocean temperatures off the west coast of South America, a phenomenon that can cause major droughts, floods, and extreme weather across the Pacific. According to Jinbao Li, a scientist at the University of Hawaii and lead author of the study published in the journal Nature Climate Change, greenhouse gases are altering the planet’s radiation balance and thus intensifying ENSO cycles. Li said the research “supports the idea that the unusually high ENSO activity in the late 20th century is a footprint of global warming.”

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The Warriors of Qiugang, a Yale Environment 360 video, chronicles a Chinese village’s fight against a polluting chemical plant. It was nominated for a 2011 Academy Award for Best Documentary Short.
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